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Author Topic: Loking for the best material to put into new deck to hold fasteners  (Read 852 times)

June 24, 2017, 01:40:08 AM
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theFunsmith

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I am in the process of ordering materials to start my deck rebuild. There will be a few points in the deck and the cap that will be subjected to stresses much greater than the rest of the build, and I would like to know what the preferred method of anchoring high stress items is. My current plan it to use Coosa for the transom and deck, but want to maximize reinforcement at the points where the T-top legs mount, and where the crab winch floor socket will mount. On the cap, I will be mounting a lateral support for the winch, and a large anchor mount (in the Pacific northwest we fish rivers at anchor requiring a much larger and different style anchor than I am seeing placed in the average 222 on here).  Is there a base/core material better than Coosa I should be adding to the deck under these points? I don't want screws pulling loose, and any advice on materials or preferred anchors other than screws, where through bolting isn't an option, is much appreciated.

June 24, 2017, 04:04:08 AM
Reply #1

mshugg

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Re: Loking for the best material to put into new deck to hold fasteners
« Reply #1 on: June 24, 2017, 04:04:08 AM »
You'll see a variety of techniques used.  I think that a preferred method, where there is access, is through bolting with backing plates to distribute the stress.  In areas without access, many glass aluminum plates to the underside of stress points.  The aluminum plate is drilled and tapped for fasteners. 

Coosa  is a great material with excellent compression strength.  That's why it's used so much as a transom material.  If you can through bolt, properly encapsulated,  Coosa should be fine for the kinds of applications that you describe.  It may be overkill for an entire deck, but there's no question it's lighter than plywood and plenty strong.  Many use a lower density foam like divynicel or a honeycomb plastic like nidacore for their decks.  You could still build in Coosa pads at stress points where you can throughbolt.

Some builders are trying sipomething new.  They're installing solid glass pads and either drilling and tapping into it or useing self tapping screws to install t tops and similar hardware.  There is some engineering data that indicates this is quite strong and has the advantage of eliminating the corrosion of dissimilar metals like SS bolts and aluminum plate.

  Dirtwheels 222 is one example of this technique in use https://classicaquasport.com/smf/index.php?topic=13425.0  I'm useing this on my rebuild as well.  I'll let you know how it works out.

There are numerous variations of these techniques.  Some find a way to tie t top mounts into stringers.  It's also a good idea to drill holes oversize and fill with thickened epoxy in order to protect the core from water.  Part of the fun of doing a rebuild is figuring this stuff out.




May 17, 2018, 12:42:22 PM
Reply #2

GoneFission

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Put backing plates under the deck where the t-top mounts. 
Cap'n John
1980 22-2 CCP
Mercury 200 Optimax 
ASPA0345M80I
"Gone Fission"
ClassicAquasport Member #209


May 17, 2018, 06:30:15 PM
Reply #3

Woodeneye

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Coosa will be just fine for thru bolting. It and similar is used where winches are attached to yacht decks. And they are under some serious load. The advice of drilling oversize holes then filling with thickened epoxy (with fibres added) is sound as it has been researched & discovered  the hard way by the brave souls gone before you. Backing plates and/or extra glass reinforcement is best practice. Remember to isolate thru bolts or screw threads from aluminium with a suitable product to isolate from corrosion. You may want to get them out one day. Have at it.
*SOLD*1981 222 CCP, Westport, MA.

May 17, 2018, 07:49:26 PM
Reply #4

RickK

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Seems like you have all the answers you need - thru-bolting +1 . A t-top is hard on the attachment points.
Rick
1971 "170" with 115 Johnson (It's usable but not 100% finished)

1992 230 Explorer with 250 Yamaha

May 17, 2018, 09:16:24 PM
Reply #5

dirtwheelsfl

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Remember to isolate thru bolts or screw threads from aluminium with a suitable product to isolate from corrosion. You may want to get them out one day.

TEFGEL!

Thats why i prefer tapping into glass. Thrubolting is number 1 though if youve got the access...

 

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